Ladder warning device



Jan. 10, 1967 N. WELLER 3,298,012

LADDER WARNING DEVICE Filed Sept. 23, 1964 FIG 2 LOW VOLTAGE TSOURCEINVENTOR.

NEWTON WELLER BY g 2 ATTORNEY 3,298,012 LADDER WARNING DEVICE NewtonWeller, P.O. Box 131, West Des Moines, Iowa 50265 Filed Sept. 23, 1964,Ser. No. 398,681 8 Claims. (Cl. 340-272) This invention relates to awarning or signalling de- -vice and more particularly to such a devicefor use in connection with ladders and the like to give a warning whenan unauthorized person attempts to climb the ladder.

Ladders are commonly used in connection with water towers, radio and TVtowers, grain elevators, fire escapes, etc. so that authorizedindividuals can climb the structures in order to maintain or repairthem. In the case of fire escapes on buildings and the like, of course,the ladders are used for safety reasons and to comply with building andfire codes. Ladders on all such structures, however, make it easy forvandals and other trespassers to deface and damage the structures,resulting in financial loss to the owners and their insurers. Inaddition, the ladders may be considered attractive nuisances forchildren, who do not recognize the dangers involved in playing on suchstructures, and the owners may therefore be liable for injury tochildren playing on such structures unless reasonable precautions aretaken.

There are not known to me any warning devices for use on thesestructures which will give a signal or warning in the event anunauthorized person climbs the ladder.

A warning device of this type should be foolproof and incapable of beingrendered inoperative even by a careful trespasser. Moreover, suchdevices should be convenient to use so that they need not be reset onthe site of the structure once they have been activated. This isespecially important where the tower or the like is located in a remotearea.

It is, therefore, an object of my invention to provide a warning deviceand signal system for use in connection with ladders and the like whichmakes it virtually impossible for an intruder or trespasser to climb theladder without activating the device and thereby giving a warning. If anintruder attempts to deactivate the device, this will also sound analarm. The device issuch that in many cases, the intruder will activateit without knowing it; The device is also completely weatherproof andwill not become inoperative under even the most adverse weatherconditions. Furthermore, a feature of my novel device and system is thatit automatically resets itself and therefore eliminates the necessity oftraveling to the site of the structure in order to activate the device.The device is simple, inexpensive, and will remain operative for manyyears with practically no maintenance.

These and other objects and features of my invention will be readilyapparent from a consideration of the following description taken inconnection with the accompanying drawings in which:

FIG. 1 is a front elevational view of a portion of a ladder showing mynovel device installed thereon;

FIG. 2 is a side elevational view with a portion of the side piece ofthe main ladder removed in order to show details of my device;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 1 and showingthe mounting for the switch;

FIG. 4 is a sectional view taken on the line 4-4 of FIG. 1 and showing amethod of retaining the signal ladder in place; and

FIG. 5 is a schematic wiring diagram of an electrical signal system thatcan be used in connection with my novel device.

Referring now to the drawings, the main ladder is of any suitableconstruction and has the usual vertical United States Patent 0 3,298,012Patented Jan. 10, 1967 side members 12 extending parallel to each other,the side members 12 being joined by a plurality of cross pieces 14commonly referred to as steps or rungs. The main ladder 10, of course,is the structure upon which a person climbs placing his hands and feeton the rungs 14 in the usual well-known manner.

Secured to the main ladder 10 for limited vertical movement with respectthereto is the actuating means re ferred to hereinafter as the signalladder 16 which is, in effect, a small ladder whose width is slightlyless than the distance between the side members 12. The signal ladder 16therefore also has vertical uprights 18 joined by cross members 20. Thecross members 20 are spaced apart at approximately the same ce-nter-tocenter distance as the rungs 14 of the main ladder 10. The signal ladder16 is held closely adjacent to the main ladder 10 by retaining meanssuch as brackets 22 which encircle the side members 12 of the mainladder 10 and the vertical uprights 18 of the signal ladder 16. Thebrackets 22 are secured tightly to the side members 12 but the verticaluprights 18 are free to move up and down within the brackets 22. Also,to hold the signal ladder 16 close to the main ladder 10, brackets 24encircle the rungs 14 and the cross members 20 but permit limitedvertical movement of the signal ladder 16 with respect to the mainladder 10.

The signal ladder 16 is suspended from a rung 14 of the main ladder 10by hangers 26 to which are connected resilient members such as springs28 and flexible members such as chains 30. The signal ladder 16 ispreferably suspended behind the main ladder 10 thus partially hiding itfrom the view of a person climbing the main ladder 10. The lower end ofthe chains 30 are connected to the uppermost cross member 20 of thesignal ladder 16. The length of the chains 30 are such that with noexternal force applied to the signal ladder 16 it will hang with the topedge of each cross member 20 slightly above the top edge of thecorresponding rung 14 of the main ladder 10. The signal ladder 16 shouldbe of a sufi'icient length, several feet or more, to make it impossiblefor an individual to climb the main ladder 10 without either stepping onor grasping and depressing one of cross members 20. The tension of thesprings 28 should be such that the weight of ice, birds, etc., will notbe sufficient to move the signal ladder 16. The total weight of thesignal ladder 16 itself is very light, and, therefore, it preferably isconstructed of lightweight corrosion-resistant materials such asaluminum.

From the description thus far, it will be obvious that any one climbingthe main ladder 10 cannot do so without either stepping on or graspingthe cross members 20 of the signal ladder 16 and thereby moving thesignal ladder 16 slightly downwardly. The cross members 20 and the rungs14 are overlapped, such as shown in FIG. 1, or the distance between themis such that an individual cannot get his hands or feet between themwithout raising the signal ladder 16. Therefore, the signal ladder 16will be moved either up or down by a trespasser climbing the ladder, andthis movement is used to give a perceptible signal. The signal can beproduced in many ways but I prefer to mount a small mercury switch 32inside of a protective enclosure 34 that is supported by means of aU-shaped bracket 36 on top of one of the rungs 14, preferably the samerung from which the signal ladder 16 is suspended. The opening in theU-bracket 36 is slightly larger than the rung 14 so that the enclosure34 containing the mercury switch 32 is free to turn on the rung 14. Arod 38 is pivotally connected at its lower end to the top cross member20 of the signal ladder 16 and is connected at its upper end to a flange40 extending outwardly from the enclosure 34. The rod 38 can be cononected to the flange 40 in any suitable manner such as by means of twonuts 42 threaded on the end of the rod 38, one nut on each side of theflange 40. Sufficient clearance should be provided between the flange 40and the nuts 42 to permit the enclosure 34 to pivot without binding onthe rod 38. The position of nuts 42 is adjusted so that when the signalladder 16 is in its normal position with the top edges of the crossmembers 20 slightly above the tops of the rungs 14, the enclosure 34will be level thus maintaining the mercury switch 32 also level. Themercury switch 32 is preferably of the type which has two contacts whichare connected by the ball of mercury when the switch 32 is in a levelposition. If the switch 32 is tilted in either direction, the mercurywill roll to one end of the switch 32 breaking the connection betweenthe two contacts. Switches of this type are well known to those skilledin the art. Obviously, the same result could be accomplished by use oftwo mercury switches each with both contacts at one end of the switch,or by the use of any other suitable type of switch, such as a limitswitch.

It should be noted that if the signal ladder 16 is moved, it will returnto its initial position by force of gravity or by action of springs 28.Thus, the mercury switch 32.

will always automatically be reset to close the cont-acts after theexternal force is released from the ladder 16.

From the description thus far, it will be obvious that when a personclimbs the main ladder 10 and thereby forces the signal ladder 16 eitherupwardly or downwardly, the rod 38 will cause the mercury switch 32 totilt thus breaking the connection normally maintained closed by theswitch 32. This breaking of the connection, when the switch 32 is tiedin a circuit, can be used to sound a visual or audible alarm on theprotected structure itself or at some remote location. The type of alarmor signal forms no part of my invention since such alarms and signalsand the circuits therefor are well known to those skilled in the art.However, for purposes of illustration, I have shown in FIG. a schematicdiagram of a circuit which is suitable for use with an alarm on the siteof the structure. If the alarm is located at a remote station, it can betied in with a circuit leased from the telephone company. The circuitemployed in either case is preferably a low-voltage, low-amperage typeand therefore is subject to the less restrictive requirements of mostelectrical codes. In the illustrative diagram of FIG. 5, the circuit issupplied from a low-voltage source with the mercury switch 32 normallyclosed and completing the circuit. The indicator or alarm 44 is inparallel with the mercury switch 32, but the alarm is not normallyenergized because the coil 48 of a control relay CR1 holds open a set ofnormally-closed contacts 46 that are in series with the alarm 44.Therefore, as long as the mercury switch 32 remains closed and the coil48 thereby energized, contacts 46 will remain open and the alarm orsignal 44 will not be energized. However, if the mercury switch 32 isopened, coil 48 will become de-energized and contacts 46 will closethereby completing the circuit to the alarm 44. Simultaneously withclosing of contacts 46, the coil 50 of a second control relay CR2 willbecome energized closing normally-open contacts 52 to complete a holdingcircuit which will maintain the circuit to the alarm 44 even if themercury switch 32 closes immediately after it was opened. Thus, withthis circuit, the mercury switch need be opened only momentarily and thealarm 44 will continue to be given indefinitely. In order to shut offthe alarm, I provide a push-button switch 54 which will break thecircuit to the alarm 44 and also break the holding circuit. Thus, when aWatchman on the site or at the remote alarm station manually operatesswitch 54, the circuit will return to its initial condition and willremain in that condition until the mercury switch 32 is again opened. Ofcourse, circuits other than that shown in FIG. 5 could be used so thatthe alarm would stop after a timed interval, for example.

It will be obvious from the above description that I have provided afoolproof alarm system for preventing unauthorized individuals fromclimbing a ladder. The signal ladder 16 cannot be climbed around if madesufliciently high, and if the signal ladder 16 is either raised orlowered or if someone attempts to remove it, the mercury switch 32 willbe opened sounding the alarm continuously on the site or at a remotestation until the alarm is manually shut off. Whether raised or loweredthe signal ladder 16 will automatically reset itself in proper positionby reason of the springs 28 which will also return the mercury switch 32to a level position and thus close the alarm circuit. Thus, if the alarm44 is located at a remote station, it is not necessary to travel to thesite to reset the system or the device regardless of the number of timesthe circuit is opened and the alarm operated. The device and the systemis extremely simple and very inexpensive to manufacture, and even underall types of adverse weather conditions will remain operative. Forexample, formations of ice will not render the device inoperativebecause they would be broken by the relative movement between the signalladder 16 and the main ladder 10. If an authorized person desirestoclimb the ladder, he merely has to call the remote station to let themknow that the alarm will be sounded or provision can be made todeactivate it on the site.

Having thus described my invention, it will be obvious to those skilledin the art that various revisions and modifications can be made in theillustrated embodiment of the device and system without departing fromthe spirit and scope of the invention. It is my intention, however, thatany such revisions and modifications as are obvious to those skilled inthe arts will be included within the scope of the following claims.

I claim:

1. A warming device for a main ladder or the like having steps which aperson can climb, said warning device comprising a signal ladder havingcross-members positioned adjacent said main ladder with the top surfacesof said cross-members normally slightly above the top surfaces of theadjacent corresponding steps of the main ladder, resilient support meansfor said signal ladder which provides for limited vertical movement ofsaid signal ladder while maintaining it in its normal position in theabsence of any external force thereon, and signal means operable bymovement of said signal ladder from its normal position.

2. The warning device of claim 1 in which said signal ladder issuspended from a step of said main ladder.

3. The warning device of claim 1 in which said signal means includes anelectrical circuit containing a mercury switch and an indicator, saidswitch being mounted on said main ladder and an operating rodinterconnecting said switch and said signal ladder so that said switchis operated by movement of said signal ladder, said indicator giving aperceptible signal in response to operation of said switch.

4. A warning device for a ladder or the like having a plurality of stepswhich a person can climb, said warning device comprising an actuatingmember positioned closely adjacent each of a plurality of consecutivesteps of said ladder, each of said members being of a widthsubstantially the same as the corresponding one of said steps andnormally positioned so as to be engaged and moved by a person climbingthe ladder and grasping or stepping on one of said steps, said actuatingmembers being connected together and movable as an actuating unit,resilient support means for said actuating unit which maintains saidactuating members in normal position while providing for limitedmovement of said unit, and signal means operatively connected to saidactuating unit and operable by movement of an actuating member from itsnormal position.

5. The warning device of claim 4 in which said actuating unit comprisesa second ladder mounted behind 5 the other ladder and having a pluralityof cross-members positioned adjacent the steps of said other ladder withthe top surfaces of said cross-members slightly above the top surfacesof the corresponding steps.

6. The warning device of claim 5 in which said resilient support meansincludes guide means to maintain said second ladder closely adjacent theother ladder and limit relative movement between said ladders tovertical movement.

7. The warning device of claim 6 in which said signal means includes anelectrical circuit containing a switch and an indicator, said switchbeing mounted on said ladders so as to be operated by relative movementbetween said ladders, said indicator giving a perceptible signal inresponse to operation of said switch.

6 8. The warning device of claim '7 in which said switch is located atthe upper end of said actuating unit.

References Cited by the Examiner UNITED STATES PATENTS NEIL C. READ,Primary Examiner.

R. M. GOLDMAN, Assistant Examiner.

1. A WARNING DEVICE FOR A MAIN LADDER OR THE LIKE HAVING STEPS WHICH APERSON CAN CLIMB, SAID WARNING DEVICE COMPRISING A SIGNAL LADDER HAVINGCROSS-MEMBERS POSITIONED ADJACENT SAID MAIN LADDER WITH THE TOP SURFACESOF SAID CROSS-MEMBERS NORMALLY SLIGHTLY ABOVE THE TOP SURFACES OF THEADJACENT CORRESPONDING STEPS OF THE MAIN LADDER, RESILIENT SUPPORT MEANSFOR SAID SIGNAL LADDER WHICH PROVIDES FOR LIMITED VERTICAL MOVEMENT OFSAID SIGNAL LADDER WHILE MAINTAINING IT IN ITS NORMAL POSITION IN THEABSENCE OF ANY EXTERNAL FORCE THEREON, AND SIGNAL MEANS OPERABLE BYMOVEMENT OF SAID SIGNAL LADDER FROM ITS NORMAL POSITION.